1. Field of the Invention
The present invention relates to an airtight container of which internal pressure has been reduced, an image displaying apparatus which uses the airtight container, and a television apparatus which uses the image displaying apparatus.
2. Description of the Related Art
A flat-panel image displaying apparatus using a field-emission electron-emitting device or a surface conduction electron-emitting device has been known. In general, the electron-emitting device is operated in an atmosphere (vacuum) which has a degree of vacuum higher than about 10−4 Pa and of which the internal pressure has been reduced. For this reason, an airtight container (i.e., a vacuum container) which has an atmospheric pressure resisting structure is necessary for the image displaying apparatus using the electron-emitting device. Here, since external force (atmospheric pressure) caused by a difference between an external pressure (atmospheric pressure) and an internal pressure (vacuum) is applied to the airtight container, the airtight container is compressed and thus deformed by the external force. More specifically, if the airtight container is excessively deformed, there is a possibility that relative positions of the electron-emitting device and a light emitter provided within the airtight container vary. Also, there is a possibility that the glass of the airtight container is broken because a stress concentrates on the surface of the glass. On the other hand, in recent years, a load to the airtight container tends to increase according as the screen of the flat-panel image displaying apparatus enlarges in size. For this reason, an image displaying apparatus which contains spacers for maintaining a space within an airtight container thereof has been proposed.
Hereinafter, a typical example of an airtight container of an image displaying apparatus in which an electron-emitting device is used will be described with reference to FIGS. 2A and 2B. More specifically, FIG. 2A is the two-dimensional schematic diagram illustrating an airtight container 99 in which spacers 4 and a frame 3 are visibly and schematically shown, and FIG. 2B is the cross section schematic diagram of the airtight container 99 viewed along the 2B-2B line indicated in FIG. 2A. The airtight container 99 includes a front substrate 1 on which a light emitter 5 such as a phosphor or the like and an anode 7 such as a metal back or the like are provided, a rear substrate 2 on which an electron source 6 is provided and which is arranged opposite to the front substrate 1, and a frame 3 which connects the front substrate 1 and the rear substrate 2 with each other at their peripheries. Each of the front substrate 1 and the rear substrate 2 is typically made of a glass plate. Further, within an internal space 98 of the airtight container 99 formed by the front substrate 1, the rear substrate 2 and the frame 3, the plate spacers 4 are arranged between the front substrate 1 and the rear substrate 2. Here, the frame 3 includes a frame member consisting of glass, metal or the like, and a bonding member consisting of frit, low-melting metal or the like. Further, the bonding member has a sealing function for connecting the front substrate 1, the rear substrate 2 and the frame member with others.
In recent years, thinning and lightening of the flat-panel image displaying apparatus has accelerated. Under the circumstances, it is required to further reduce the thickness of the glass plate constituting the front substrate 1 and the rear substrate 2. In this connection, Japanese Patent Application Laid-Open No. 2002-358915 and Japanese Patent Application Laid-Open No. H10-254375 respectively disclose a technique of making the height of a frame higher than the height of a spacer.